Insulation film and method for making insulation film

ABSTRACT

The present invention provides an insulation film, comprising a film upper layer and a film lower layer, wherein both of the film upper layer and film lower layer are made of a PC or PET material, the PC or PET material contains a flame retardant to meet the flame retardance and puncture resistance property thereof; a film intermediate layer located between the film upper layer and the film lower layer, the film intermediate layer is made of the blends of PP and/or PE and PC and/or PET; an upper surface of the film intermediate layer is bound together with a lower surface of the film upper layer, a lower surface of the film intermediate layer is bound together with an upper surface of the film lower layer.

FIELD OF THE INVENTION

The present invention relates to an insulation film, and particularly toan insulation film made of PC or PET.

BACKGROUND OF THE INVENTION

An insulation film is used to isolate various electronic devices orcomponents to avoid malfunction caused by short-circuiting, breakdown orthe like between the electronic devices or components, or electronicelements in the electronic devices or components, and reduce the risk ofcatching fire of the electronic devices or components so as to guaranteenormal operation of various electronic elements. For example, theinsulation film is placed between a printed circuit hoard (PCB)containing various circuits and a metallic housing such as an aluminumor copper housing for preventing EMI (electromagnetic interference) toprevent problems such as shortcricuiting caused by contact between thevarious elements on the PCB and the metallic housing. In order to usethe insulation film, the insulation film is required to have propertiessuch as flame retardance and resistance against long-term hightemperature. Furthermore, specific indices for the requirements forthese properties of the insulation film vary with different requirementsfor insulation.

Since the raw material of PC and PET have good puncture resistanceproperty, insulation films made of PC or PET are widely used. However,the folding endurance property of PC and PET is not good, and therefore,the PC and PET will be torn when being folded.

Therefore, it is desired to produce a insulation film having both goodpuncture strength and good folding endurance property.

SUMMARY OF THE INVENTION

The present invention provides an insulation film, comprising a filmupper layer and a film lower layer, wherein both of the film upper layerand film lower layer are made of a PC or PET material, the PC or PETmaterial contains a flame retardant to meet the flame retardance andpuncture resistance property thereof; a film intermediate layer locatedbetween the film upper layer and the film lower layer, the filmintermediate layer is made of the blends of PP and/or PE and PC and/orPET; an upper surface of the film intermediate layer is bound togetherwith a lower surface of the film upper layer, a lower surface of thefilm intermediate layer is bound together with an upper surface of thefilm lower layer. The film upper layer and the film lower layer are madeof like or identical material. The flame retardant in the film upperlayer and the film lower layer contains a phosphor-containing flameretardant or a silicon-containing flame retardant or abromine-containing flame retardant or a chlorine-containing flameretardant. The PC or PET in the film upper layer and the film lowerlayer accounts for 75%-99.7% of a mass of the film upper layer or filmlower layer, and the flame retardant accounts for 0.3%-25% of the massof the film upper layer or the film lower layer. Because the upper layerand the lower layer of the insulation film are made of PC or PET whichis rigid, the puncture strength of the insulation film is substantiallyguaranteed. When thickness of the intermediate layer accounts for 5%-20%of the total thickness of the insulation film of the present invention,compared with the single-layered PCT or PET material having a samethickness with the insulation film of the present invention, thepuncture strength of insulation film of the present invention decreasesnot obviously (only decreases by 1%˜10%). On the other hand, because theintermediate layer made of the blends of PP and/or PE and PC and/or PETcomprises PP and/or PE, the insulation film of the present invention hasgood folding endurance. Compared with the single-layered PC or PETmaterial having a thickness of 0.4 mm, the foldability of the insulationfilm 100 having the same thickness of 0.4 mm according to the presentinvention is raised from 10-20 times to not less than 30 times under thetest method of ASTM D2176-97a. Such folding endurance can meet theprocessing requirements. Therefore, the present invention provides amulti-layered insulation film having both good puncture strength andgood folding endurance. The thickness of the film intermediate layer is5%-50% of the thickness of the insulation film, and the thickness of thefilm upper layer and the film lower layer is 50%-95% of a totalthickness of the insulation film. The total thickness of the insulationfilm is in a range of 0.05 mm-3.0 mm. The insulation film is formed by aco-extruding process or a composite process.

The present invention further provides a method of producing theinsulation film. The method comprises: on a first extruder, extruding PCor PET particles containing the flame retardant to melt them, the PC orPET containing the flame retardant in a molten state flowing out of thefirst extruder and then through subsequent connecting pipes into adispenser, the dispenser dividing the PC or PET containing the flameretardant in the molten state extruded out of the first extruder intotwo sections, namely, a first molten PC or PET containing the flameretardant and a second molten PC or PET containing the flame retardant;extruding on a second extruder the particles of the blends of PP and/orPE and PC and/or PET to make them molten, the blends of PP and/or PE andPC and/or PET in the molten state flowing out of the second extruder andthen through subsequent connecting pipes into the dispenser, the blendsof PP and/or PE and PC and/or PET in the molten state flowing intobetween the first molten PC or PET containing the flame retardant andthe second molten PC or PET containing the flame retardant in thedispenser; the first molten PC or PET containing flame retardant, theblends of PP and/or PE and PC and/or PET in the molten state and thesecond molten PC or PET containing flame retardant being superimposedtogether and then flowing out of the dispenser, flowing through a diehead into a cooling forming roller to be cooled and formed as asheet/film.

The present invention further provides a method of producing theinsulation film. The method comprises: on a first extruder, extruding PCor PET particles containing the flame retardant to melt them to form afirst molten PC or PET containing the flame retardant, the first moltenPC or PET containing the flame retardant flowing out of the firstextruder and then through subsequent connecting pipes into a dispenser;extruding on a third extruder PC or PET particles containing the flameretardant to make them molten to form a second molten PC or PETcontaining the flame retardant, the second molten PC or PET containingthe flame retardant being extruded out of the third extruder and thenflowing through subsequent connecting pipes into the dispenser;extruding on a second extruder the blends of PP and/or PE and PC and/orPET to make them molten, the blends of PP and/or PE and PC and/or PET inthe molten state flowing out of the second extruder and then throughsubsequent connecting pipes into the dispenser, the blends of PP and/orPE and PC and/or PET in the molten state flowing into between the firstmolten PC or PET containing the flame retardant and the second molten PCor PET containing the flame retardant in the dispenser; the first moltenPC or PET containing flame retardant, the blends of PP and/or PE and PCand/or PET in the molten state and the second molten PC or PETcontaining flame retardant being superimposed together and then flowingout of the dispenser, flowing through a die head into a cooling formingroller to be cooled and formed as a sheet/film.

The present invention further provides a method of producing theinsulation film. The method comprises: providing the film upper layerand the film lower layer, wherein both of the film upper layer and filmlower layer are made of a PC or PET material and the PC or PET materialcontains a flame retardant; providing an intermediate layer locatedbetween the film upper layer and the film lower layer, the filmintermediate layer is made of the blends of PP and/or PE and PC and/orPET; applying a glue to a lower surface of the film upper layer and/oran upper surface of the film intermediate layer, and applying a glue onan upper surface of the film lower layer and/or a lower surface of thefilm intermediate layer; delivering the film upper layer, filmintermediate layer and film lower layer through pressing rollers to bepressed and formed as a sheet/film.

The present invention further provides a method of producing theinsulation film. The method comprises: providing the film upper layerand the film lower layer, wherein both of the film upper layer and filmlower layer are made of a PC or PET material and the PC or PET materialcontains a flame retardant; providing an intermediate layer locatedbetween the film upper layer and the film lower layer, the filmintermediate layer is made of the blends of PP and/or PE and PC and/orPET; respectively heating the film upper layer, the film intermediatelayer and the film lower layer to soften them; delivering the heated andsoftened film upper layer, film intermediate layer and film lower layerthrough pressing rollers to be pressed and formed as a sheet/film.

The present invention provides another insulation film, comprising: afilm upper layer made of a PC or PET material, wherein the PC or PETmaterial contains a flame retardant; and a film lower layer, wherein thefilm lower layer is made of the blends of PP and/or PE and PC and/orPET; a lower surface of the film upper layer is bound together with anupper surface of the film lower layer. The flame retardant in the filmupper layer contains a phosphor-containing flame retardant or asilicon-containing flame retardant or a bromine-containing flameretardant or a chlorine-containing flame retardant. The PC or PET in thefilm upper layer accounts for 75%-99.7% of a mass of the film upperlayer, and the flame retardant accounts for 0.3%-25% of the mass of thefilm upper layer. The PP and/or PE in the film lower layer accounts for5%-95% of a mass of the film lower layer, the PC and/or PET in the filmlower layer accounts for 4.5%-94.7% of a mass of the film lower layerand the additives in the film lower layer accounts for 0.3%-20% of amass of the film lower layer. The total thickness of the insulation filmis in a range of 0.05 mm-3.0 mm. The insulation film is formed byprocessing by a co-extruding process or a composite process.

The present invention further provides an insulation film, comprisingtwo PC or PET layers containing the flame retardant and one layer madeof the blends of PP and/or PE and PC and/or PET, wherein the two PC orPET layers containing the flame retardant are respectively boundtogether with an upper surface and a lower surface of the layer made ofthe blends of PP and/or PE and PC and/or PET. The flame retardant in thePC or PET layers containing the flame retardant contains aphosphor-containing flame retardant or a silicon-containing flameretardant or a bromine-containing flame retardant or achlorine-containing flame retardant. The PC or PET accounts for75%-99.7% of a mass of the PC or PET layers containing the flameretardant, and the flame retardant accounts for 0.3%-25% of the mass ofthe PC or PET layers containing the flame retardant. The PP and/or PE inthe layer made of the blends of PP and/or PE and PC and/or PET accountsfor 5%˜95% of a mass of the layer made of the blends of PP and/or PE andPC and/or PET, the PC and/or PET in the layer made of the blends of PPand/or PE and PC and/or PET accounts for 4.5%˜94.7% of a mass of thelayer made of the blends of PP and/or PE and PC and/or PET and theadditives in the layer made of the blends of PP and/or PE and PC and/orPET accounts for 0.3%˜20% of a mass of the layer made of the blends ofPP and/or PE and PC and/or PET. When thickness of the intermediate layeraccounts for 5%˜20% of the total thickness of the insulation film of thepresent invention, compared with the single-layered PCT or PET materialhaving a same thickness with the insulation film of the presentinvention, the puncture strength of insulation film of the presentinvention decreases not obviously (only decreases by 1%˜10%). Comparedwith the single-layered PC or PET material having a thickness of 0.4 mm,the foldability of the insulation film having the same thickness of 0.4mm according to the present invention is raised from 10˜20 times to noless than 30 times under the test method of ASTM D2176-97a. Thethickness of the layer made of the blends of PP and/or PE and PC and/orPET is 5%-50% of the thickness of the insulation film, and a total ofthe thickness of the two PC or PET layers containing the flame retardantis 50%-95% of a total thickness of the insulation film. The totalthickness of the insulation film is in a range of 0.05 mm-3.0 mm. Theinsulation film is formed by a co-extruding process or a compositeprocess.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of an insulation film containing a flameretardant according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of the insulation film containing aflame retardant of FIG. 1 taken along the line A-A in FIG. 1;

FIG. 3 is a schematic view of an insulation film containing a flameretardant according to another embodiment of the present invention;

FIG. 4 is a cross-sectional view of the insulation film containing aflame retardant of FIG. 3 taken along the line B-B in FIG. 3;

FIG. 5 is an exemplary view of a co-extruding process for producing theinsulation film according to an embodiment of the present invention;

FIG. 6 is an exemplary view of another co-extruding process forproducing the insulation film according to an embodiment of the presentinvention;

FIG. 7 is an exemplary view of a composite process for producing theinsulation film according to an embodiment of the present invention;

FIG. 8 is an exemplary view of a composite process for producing theinsulation film according to an embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates a schematic view of an insulation film 100 accordingto an embodiment of the present invention. According to one embodimentof the present invention, the insulation film 100 has a thickness of0.05 mm-3.0 mm. FIG. 2 is a cross-sectional view of the insulation film100 of FIG. 1 taken along the line A-A in FIG. 1. As shown in FIG. 2,the insulation film 100 comprises an upper layer 101, an intermediatelayer 102 and a lower layer 103. According to an embodiment of thepresent invention, a thickness of the upper layer 101 and the lowerlayer 103 of the insulation film is 50-95% of the thickness of theinsulation film, and a thickness of the intermediate layer of theinsulation film is 5%-50% of the thickness of the insulation film.

The upper layer 101 and the lower layer 103 of the insulation film 100are made of PC or PET containing a flame retardant. The flame retardantin the upper layer 101 and the lower layer 103 of the insulation film100 comprises a phosphor-containing flame retardant or asilicon-containing flame retardant or a bromine-containing flameretardant or a chlorine-containing flame retardant. According to anembodiment of the present invention, a mass of the flame retardant inthe upper layer 101 and the lower layer 103 of the insulation film 100is 0.3%-25% of a mass of the upper layer 101 or the lower layer 103 ofthe insulation film and a mass of the PC or PET material in the upperlayer 101 and the lower layer 103 of the insulation film 100 is75%-99.7% of a mass of the upper layer 101 or the lower layer 103 of theinsulation film so that the insulation film 100 has good flameretardance and good puncture strength. The intermediate layer 102 of theinsulation film 100 is made of the blends of PP and/or PE and PC and/orPET. Since the blends of PP and/or PE and PC and/or PET of theintermediate layer 102 of the insulation film 100 contains PP and/or PE,the insulation film 100 has good folding endurance. The mass of the PPand/or PE accounts for 5%˜95% of the mass of the intermediate layer 102,the mass of the PC and/or PET accounts for 4.5%˜94.7% of the mass of theintermediate layer 102 and the additives accounts for 0.3%˜20% of themass of the intermediate layer 102.

Because the insulation film 100 of the present invention has a layermade of the blends of PP and/or PE and PC and/or PET, the insulationfilm 100 of the present invention has the following advantages:

Because the upper layer 101 and the lower layer 103 of the insulationfilm are made of PC or PET which is rigid, the puncture strength of theinsulation film is substantially guaranteed. When thickness of theintermediate layer accounts for 5%˜20% of the total thickness of theinsulation film of the present invention, compared with thesingle-layered PCT or PET material having a same thickness with theinsulation film of the present invention, the puncture strength ofinsulation film of the present invention decreases not obviously (onlydecreases by 1%˜10%). On the other hand, because the intermediate layermade of the blends of PP and/or PE and PC and/or PET comprises PP and/orPE, the insulation film of the present invention has good foldingendurance. Compared with the single-layered PC or PET material having athickness of 0.4 mm, the foldability of the insulation film 100 havingthe same thickness of 0.4 mm according to the present invention israised from 10˜20 times to not less than 30 times under the test methodof ASTM D2176-97a. Such folding endurance can meet the processingrequirements. Therefore, the present invention provides a multi-layeredinsulation film having both good puncture strength and good foldingendurance.

Furthermore, the Inventor found that the current regulatory standards(e.g., the international standard UL-60950 or IEC-60950) for theinsulation film requires at least a thickness of 0.4 mm for asingle-layered insulation film made of a homogeneous material ifsupplementary insulation or reinforced insulation is required for thesingle-layered insulation film. However, the UL standard does not imposesuch requirement of thickness for a multi-layered insulation filmcomprising inseparable layers, but the UL standard requires the voltageresistance of the multi-layered insulation film comprising inseparablelayers to increase by 50%˜100% and requires the multi-layered insulationfilm comprising inseparable layers to pass the additional Mandrel test.That is to say, even if a multi-layered insulation film comprisinginseparable layers has a thickness of less than 0.4 mm, it is consideredas meeting the regulatory standards so long as it passes the strictervoltage withstanding test and the additional Mandrel test. Theinsulation film of the present invention is a multi-layered insulationfilm having inseparable multiple layers which are made of differentmaterials, and it is found after experiments that the material for theinsulation film of the present invention can exactly pass the strictervoltage withstanding test and the additional Mandrel test. Therefore, tomeet the requirement under the regulatory standards, the thickness ofthe insulation film may be less than 0.4 mm. In other words, as comparedwith the conventional single-layered PC or PET insulation filmcontaining the flame retardant, the insulation film according to thepresent invention has a reduced thickness, for example, the thickness ofthe insulation film can be reduced from 0.43 mm to 0.25 mm or thinner,while the insulation film according to the present invention can passthe stricter voltage withstanding test and the additional Mandrel test,thereby saving the material and cutting the production costs.

FIG. 3 is a schematic view of a film 200 according to another embodimentof the present invention. The only difference between the insulationfilm 200 and the insulation film 100 in FIG. 1 lies in that theinsulation film 200 has a structure of two layers, wherein one layer ismade of PC or PET containing the flame retardant and the other layer ismade of the blends of PP and/or PE and PC and/or PET. FIG. 4 is across-sectional view taken along a line B-B of FIG. 3 to illustrate thestructure of the insulation film 200 having two layers (201, 202). Thetwo-layered insulation film shown in FIG. 3 and FIG. 4 also has thelayer made of the blends of PP and/or PE and PC and/or PET, andtherefore has the same advantages of the insulation film shown in FIG. 1and FIG. 2. Certainly, the principles of the present invention alsoapply to other multi-layered insulation films made of differentmaterials.

FIG. 5 illustrates a co-extruding assembly line 500 of a co-extrudingprocess for producing the insulation film 100 according to an embodimentof the present invention. As shown in FIG. 5, the co-extruding assemblyline 500 comprises a first extruder 501 and a second extruder 502. Thefirst extruder 501 comprises a feeding hopper 509 and a receiving cavity510. The feeding hopper 509 is configured to receive PC or PET particlescontaining the flame retardant. The receiving cavity 510 is providedwith a driving screw 511. An outlet of the feeding hopper 509 iscommunicated with a front end inlet 512 of the receiving cavity 510, arear end outlet 513 of the receiving cavity 510 is communicated with aninlet of a pipe 506, and an outlet of the pipe 506 is communicated witha first inlet 514 of a dispenser 503. The second extruder 502 comprisesa feeding hopper 515 and a receiving cavity 516. The feeding hopper 515is configured to receive the particulars of the blends of PP and/or PEand PC and/or PET. The receiving cavity 516 is provided with a drivingscrew 517. An outlet of the feeding hopper 515 is communicated with afront end inlet 518 of the receiving cavity 516, a rear end outlet 519of the receiving cavity 516 is communicated with an inlet of a pipe 507,and an outlet of the pipe 507 is communicated with a second inlet 520 ofthe dispenser 503.

The first inlet 514 of the dispenser 503 is communicated with an inletof a first branch line 521 and an inlet of the second branch line 522 ofthe dispenser, and the second inlet 520 of the dispenser 503 iscommunicated with an inlet of a third branch line 523 of the dispenser.As shown in FIG. 5, the third branch line 523 is located between thefirst branch line 521 and the second branch line 522. An outlet of thefirst branch line 521, an outlet of the second branch line 522 and anoutlet of the third branch line 523 converge at an outlet 524 of thedispenser. The outlet 524 of the dispenser is connected to an inlet of aconduit 525, and an outlet of the conduit 525 is communicated with aninlet of a die cavity 526 of a die head 504. The die cavity 526 of thedie head 504 has an appropriate width and depth so that the die cavityis sufficient to receive a material delivered from the pipe of thedispenser, and the die cavity 526 is flat so that the material deliveredfrom the pipe of the dispenser is die pressed into a flat shape therein.The die pressed material is delivered through an outlet of the diecavity 526 to a forming roller apparatus 505. The forming rollerapparatus 505 comprises a plurality of forming rollers placed adjacentto one another. The material delivered from the die cavity of the diehead to the forming roller apparatus is stretched, roll pressed andcooled between the plurality of forming rollers to achieve a desiredthickness and form a sheet material. FIG. 5 shows three such formingrollers 505.1, 505.2 and 505.3. Two or more forming rollers may be usedin other embodiments.

According to the co-extruding assembly line 500 shown in FIG. 5, theinsulation film 100 according to the present invention is produced inthe following procedure:

During production, the receiving cavities 510 and 516 of the firstextruder 501 and the second extruder 502 are heated, and the drivingscrews 511 and 517 of the first extruder 501 and the second extruder 502are rotated.

The PC or PET particles containing the retardant are fed to the feedinghopper 509 of the first extruder 501. The rotation of the driving screw511 of the first extruder 501 pushes the PC or PET particles containingthe flame retardant in the feeding hopper 509 into the receiving cavity510. Since the receiving cavity 510 is heated, the PC or PET particlescontaining the flame retardant, after entry into the receiving cavity510, are melted due to heat generated from friction and are in a moltenstate. Affected by the pushing force generated by rotation of thedriving screw 511, the PC or PET containing the flame retardant in themolten state is delivered to the rear end outlet 513 of the receivingcavity 510. The pushing force generated by rotation of the driving screw511 enables the PC or PET containing the flame retardant in the moltenstate to flow out of the receiving cavity 510 from the rear end outlet513 of the receiving cavity 510, and then enters the pipe 506 throughthe inlet of the pipe 506 communicated with the rear end outlet 513 ofthe receiving cavity 510. The PC or PET containing the flame retardantin the molten state flows out through the outlet of the pipe 506 to thefirst inlet 514 of the dispenser 503. At the inlet 514 of the dispenser,the PC or PET containing the flame retardant in the molten state isdivided into two flows: one enters the first branch line 521 of thedispenser to become a first molten PC or PET containing flame retardant,and the other enters the third branch line 522 of the dispenser tobecome a second molten PC or PET containing flame retardant.

Similarly, the particles of the blends of PP and/or PE and PC and/or PETare fed to the feeding hopper 515 of the second extruder 502. Therotation of the driving screw 517 of the second extruder 502 pushes theparticles of the blends of PP and/or PE and PC and/or PET in the feedinghopper 515 into the receiving cavity 516. Since the receiving cavity 516is heated, the particles of the blends of PP and/or PE and PC and/orPET, after entry into the receiving cavity 516, are melted due to heatgenerated from friction and are in a molten state. Affected by thepushing force generated by rotation of the driving screw 517, the blendsof PP and/or PE and PC and/or PET in the molten state is delivered tothe rear end outlet 519 of the receiving cavity 516. The pushing forcegenerated by rotation of the driving screw 517 enables the blends of PPand/or PE and PC and/or PET in the molten state to flow out of thereceiving cavity 516 from the rear end outlet 519 of the receivingcavity 516, and then enters the pipe 507 through the inlet of the pipe507 communicated with the rear end outlet 519 of the receiving cavity516. The blends of PP and/or PE and PC and/or PET in the molten stateflows out through the outlet of the pipe 507 to the second inlet 520 ofthe dispenser 503, and enters the third branch line 523 of the dispenservia the second inlet 503. Noticeably, the operation for the particles ofthe blends of PP and/or PE and PC and/or PET is performed at the sametime as the previously-described operation for the PC or PET containingthe flame retardant.

The first molten PC or PET containing flame retardant entering the firstbranch line 521 of the dispenser 503, the blends of PP and/or PE and PCand/or PET in the molten state entering the third branch line 523 of thedispenser 503 and the second molten PC or PET containing flame retardantentering the second branch line 522 of the dispenser 503 converge at theoutlet 524 of the dispenser to thereby superimpose together, and thenenters the die cavity 526 of the die head 504 via the conduit 525communicated with the outlet 524 of the dispenser so that the first andsecond molten PC or PET and the blends of PP and/or PE and PC and/or PETin the molten state are die pressed in the die cavity 526 to form a flatmolten mass. The die pressed flat molten mass is delivered to betweenthe forming rollers 505.1 and 505.2 to receive a stretching and pressingforce applied by the forming rollers 505.1 and 505.2 thereto, andmeanwhile it is cooled by the forming rollers 505.1 and 505.2 to therebyform a sheet or film 100′ with a predetermined thickness. The film 100′continued to be fed between the forming rollers 505.2 and 505.3 forfurther cooling or annealing to form the insulation film or sheet 100according to one embodiment of the present invention. As needed, the diepressed flat molten mass outputted from the die head may run throughonly two forming rollers or more than two forming rollers to form thefilm.

FIG. 6 illustrates a co-extruding assembly line 600 of anotherco-extruding process for producing the insulation film 100 according toan embodiment of the present invention. As shown in FIG. 6, theco-extruding assembly line 600 comprises a first extruder 601, a secondextruder 602 and a third extruder 603. The first extruder 601, thesecond extruder 602 and the third extruder 603 respectively comprise afeeding hopper 611, 612, 613, a receiving cavity 614, 615, 616 and adriving screw 617, 618 and 619. The feeding hoppers of the first andthird extruders 611 and 613 are configured to receive PC or PETparticles containing the flame retardant. The feeding hopper of thesecond extruder 612 is configured to receive the particles of the blendsof PP and/or PE and PC and/or PET. An outlet of the feeding hopper 611of the first extruder 601 is communicated with a front end inlet 620 ofthe receiving cavity 614, a rear end outlet 624 of the receiving cavity614 is communicated with an inlet of a pipe 607, and an outlet of thepipe 607 is communicated with a first inlet 627 of a dispenser 604.Similarly, an outlet of the feeding hopper 612 of the second extruder602 is communicated with a front end inlet 622 of the receiving cavity615, a rear end outlet 625 of the receiving cavity 615 is communicatedwith an inlet of a pipe 608, and an outlet of the pipe 608 iscommunicated with a second inlet 628 of the dispenser 604. An outlet ofthe feeding hopper 613 of the third extruder 603 is communicated with afront end inlet 623 of the receiving cavity 616, a rear end outlet 626of the receiving cavity 616 is communicated with an inlet of a pipe 609,and an outlet of the pipe 609 is communicated with a third inlet 629 ofthe dispenser 604.

The first inlet 627 of the dispenser 604 is communicated with an inletof a first branch line 630 of the dispenser, a second inlet 628 of thedispenser 604 is communicated with an inlet of a second branch line 631of the dispenser, and a third inlet 629 of the dispenser 604 iscommunicated with an inlet of the of the third branch line 632 of thedispenser. As shown in FIG. 6, the second branch line 631 is locatedbetween the first branch line 630 and the third branch line 623. Anoutlet of the first branch line 630, an outlet of the second branch line631 and an outlet of the third branch line 632 converge at an outlet 633of the dispenser. The outlet 633 of the dispenser is communicated withan inlet of a conduit 634, and an outlet of the conduit 634 iscommunicated with an inlet of a die cavity 635 of a die head 605. Thedie cavity 635 of the die head 605 has an appropriate width and depth sothat the die cavity is sufficient to receive a material delivered fromthe pipe of the dispenser, and the die cavity 635 is flat so that thematerial delivered from the pipe of the dispenser is die pressed into aflat shape therein. The die pressed material is delivered through anoutlet of the die cavity 635 to a forming roller apparatus 610. Theforming roller apparatus 610 comprises a plurality of forming rollersplaced adjacent to one another. The material delivered from the diecavity of the die head to the forming roller apparatus is stretched,roll pressed and cooled between the plurality of forming rollers toachieve a desired thickness and form a sheet material. FIG. 6 showsthree such forming rollers 610.1, 610.2 and 610.3. Two or more formingrollers may be used in other embodiments.

According to the co-extruding assembly line 600 shown in FIG. 6, theinsulation film 100 according to the present invention is produced inthe following procedure:

During production, the receiving cavities 614, 615 and 616 of the firstextruder 601, the second extruder 602 and the third extruder 603 areheated, and the driving screws 617, 618 and 619 of the first extruder601, the second extruder 602 and the third extruder 603 are rotated.

The PC or PET particles containing the flame retardant are fed to thefeeding hopper 611 of the first extruder 601. The rotation of thedriving screw 617 of the first extruder 601 pushes the PC or PETparticles containing the flame retardant in the feeding hopper 611 intothe receiving cavity 614. Since the receiving cavity 614 is heated, thePC or PET particles containing the flame retardant, after entry into thereceiving cavity 614, are melted due to heat generated from friction andare in a molten state. Affected by the pushing force generated byrotation of the driving screw 617, the PC or PET containing the flameretardant in the molten state is delivered to the rear end outlet 624 ofthe receiving cavity 614. The pushing force generated by rotation of thedriving screw 617 enables the PC or PET containing the flame retardantin the molten state to flow out of the receiving cavity 614 from therear end outlet 624 of the receiving cavity 614, and then enters thepipe 607 through the inlet of the pipe 607 communicated with the rearend outlet 624 of the receiving cavity 614. The PC or PET containing theflame retardant in the molten state flows out through the outlet of thepipe 607 to the first inlet 627 of the dispenser 604, and enters thefirst branch line 630 of the dispenser 604. The PC or PET containing theflame retardant entering the first branch line 630 of the dispenser 604is a first molten PC or PET containing the flame retardant.

Similarly, the PC or PET particles containing the flame retardant arefed to the feeding hopper 613 of the third extruder 603. The PC or PETparticles containing the flame retardant are delivered into the thirdbranch line 632 of the dispenser 604 in the same manner as the PC or PETparticles containing the flame retardant in the feeding hopper 611 ofthe first extruder 601, and the PC or PET containing the flame retardantentering the third branch line 632 of the dispenser 604 is a secondmolten PC or PET containing the flame retardant.

The particles of the blends of PP and/or PE and PC and/or PET are fed tothe feeding hopper 612 of the second extruder 602. The particles of theblends of PP and/or PE and PC and/or PET are delivered into the secondbranch line 631 of the dispenser 604 in the same manner as the PC or PETparticles containing the flame retardant in the feeding hopper 611 ofthe first extruder 601.

Noticeably, operation is performed at the same time for delivering thePC or PET particles containing the flame retardant and the blends of PPand/or PE and PC and/or PET respectively to the first branch line 630,the second branch line 631 and the third branch line 632.

Similar to the extruding process in the assembly line shown in FIG. 5,the first molten PC or PET containing the flame retardant entering thefirst branch line 630 of the dispenser 604, the blends of PP and/or PEand PC and/or PET in the molten state entering the second branch line631 of the dispenser 604 and the second molten PC or PET containingflame retardant entering the third branch line 632 of the dispenserconverge at the outlet 633 of the dispenser to thereby superimposetogether, and then enters the die cavity 635 of the die head 605 via theconduit 634 communicated with the outlet 633 of the dispenser so thatthe first and second molten PC or PET and the blends of PP and/or PE andPC and/or PET in the molten state are die pressed in the die cavity 635to form a flat molten mass. The die pressed flat molten mass isdelivered to between the forming rollers 610.1 and 610.2 to receive astretching and pressing force applied by the forming rollers 610.1 and610.2 thereto, to thereby form a sheet or film 100′ with a predeterminedthickness. The film 100′ continued to be fed between the forming rollers610.2 and 610.3 for further cooling or annealing to form the insulationfilm or sheet 100 according to one embodiment of the present invention.As needed, the die pressed flat molten mass outputted from the die headmay run through only two forming rollers or more than two formingrollers to form the film.

Before the invention, there is not a precedent that the co-extrudingprocess is used for producing the insulation film. Conventionally, thethickness of the intermediate layer of the product produced by theco-extruding process accounts for a relatively high percentage of thetotal thickness of the product. In the insulation film produced by theco-extruding process according to the present invention, the thicknessof the intermediate layer accounts for a relatively low percentage ofthe total thickness of the insulation film, namely, only 5%-50% of thetotal thickness of the insulation film. By employing the co-extrudingprocess of the present invention, the respective layers can still beevenly distributed under the circumstances that the thickness of theintermediate layer accounts for a relatively low percentage of the totalthickness of the insulation film.

In the co-extruding production process shown in FIG. 5 and FIG. 6, thefirst molten PC or PET containing the flame retardant, blends of PPand/or PE and PC and/or PET in the molten state, and the second moltenPC or PET containing the flame retardant are superimposed in thedispenser. However, those skilled in the art should appreciate that thefirst molten PC or PET containing the flame retardant, the blends of PPand/or PE and PC and/or PET in the molten state, and the second moltenPC or PET containing the flame retardant may also be superimposed in thedie head.

The insulation film produced by the co-extruding process is of highquality, but the co-extruding process imposes high requirements for theapparatus. Therefore, the present invention further provides a method ofproducing the insulation film by a composite process, which imposeslower requirements for the apparatus.

FIG. 7 is a composite assembly line 700 of a composite process forproducing the insulation film 100 according to an embodiment of thepresent invention, comprising a pair of pressing rollers 704.1 and704.2. An upper layer 701, an intermediate layer 702 and a lower layer703 of the insulation film 100 are respectively wound on three deliveryrollers (not shown), and meanwhile inputted between the pressing rollers704.1 and 704.2. When the pressing rollers 704.1 and 704.2 rotaterelative to each other, a pulling force will be generated for the upperlayer 701, the intermediate layer 702 and the lower layer 703 so thatthe delivery rollers are moved to release the upper layer 701, theintermediate layer 702 and the lower layer 703 respectively for thepressing rollers 704.1 and 704.2. As such, the upper layer 701, theintermediate layer 702 and the lower layer 703 are wound between and runthrough between the pressing rollers 704.1 and 704.2 so that the upperlayer 701, the intermediate layer 702 and the lower layer 703 arepressed to form the insulation film 100.

In FIG. 7, the upper layer 701 and the lower layer 703 of the insulationfilm 100 is made of PC or PET material containing the flame retardant,and the intermediate layer 702 of the insulation film 100 is the layermade of the blends of PP and/or PE and PC and/or PET. After the upperlayer 701, the intermediate layer 702 and the lower layer 703 of theinsulation film 100 are released from respective delivery rollers andbefore they are wound between and run through the pressing rollers 704.1and 704.2, a glue is applied to a lower surface of the upper layer 701and/or an upper surface of the intermediate layer 702, and a glue isapplied on a lower surface of the intermediate layer 702 and/or an uppersurface of the lower layer 703 so that the upper layer 701, theintermediate layer 702 and the lower layer 703 of the insulation film100 are, after being pressed by the pressing rollers 704.01 and 704.02,adhered together to form the insulation film 100.

FIG. 8 is another composite assembly line 800 of a composite process forproducing the insulation film 100 according to an embodiment of thepresent invention. The composite assembly line 800 in FIG. 8 is similarto the composite assembly line 700 of FIG. 7. The only differencetherebetween is that in FIG. 8, a baker 805, 806 and 807 is respectivelyprovided on one side of a path from the respective delivery rollers foran upper layer 801, an intermediate layer 802 and a lower layer 803 ofthe insulation film 100 to between pressing rollers 804.01 and 804.02.

In FIG. 8, after the upper layer 801, the intermediate layer 802 and thelower layer 803 of the insulation film 100 are released from respectivedelivery rollers and before they are wound between and run through thepressing rollers 804.1 and 804.2, the upper layer 801, the intermediatelayer 802 and the lower layer 803 of the insulation film 100 are heatedby the respective bakers to soften them so that the upper layer 801, theintermediate layer 802 and the lower layer 803 of the softenedinsulation film 100 are, after being pressed by the pressing rollers804.01 and 804.02, adhered together to form the insulation film 100.

Although FIG. 8 only illustrates a method of heating the upper layer801, the intermediate layer 802 and the lower layer 803 of theinsulation film via the bakers, those skilled in the art shouldappreciate that the upper layer 801, the intermediate layer 802 and thelower layer 803 are softened in other manners to soften them.

It should be noted that any one value in the ranges of the valuesindicated in the present application is applicable to the presentinvention.

Although the description illustrates, describes and points out novelfeatures of the present invention applicable to preferred embodiments ofthe present invention, it should be appreciated that without departingfrom the spirit of the present invention, those skilled in the art mayomit, substitute or change the form and details of the illustratedapparatus and its operation. For example, it is particularly noticeablethat combinations of those elements and/or steps of the method forperforming the substantially the same functions in substantively samemanners to achieve the same result fall within the scope of the presentinvention. Besides, it should be appreciated that the forms disclosed inthe present invention or structures and/or members and/or steps of themethod shown and/or described in the embodiments might, as options ofdesign, be combined into other forms or embodiments. Therefore, thescope of the present invention is only limited to the scope as definedby the appended claims.

What is claimed is:
 1. A method of producing an insulation film, whereinsaid insulation film comprises: a film upper layer and a film lowerlayer, wherein the film upper layer is made of PC or PET material andthe film lower layer is made of PC or PET material, and the PC or PETmaterial contains a flame retardant to meet flame retardance thereof; afilm intermediate layer located between the film upper layer and thefilm lower layer, wherein the film intermediate layer is made of blendsof PP and/or PE and PC; and wherein an upper surface of the filmintermediate layer is bound together with a lower surface of the filmupper layer, and a lower surface of the film intermediate layer is boundtogether with an upper surface of the film lower layer, the methodcomprising: on a first extruder, extruding PC or PET particlescontaining the flame retardant to melt them, the PC or PET containingthe flame retardant in a molten state flowing out of the first extruderand then through subsequent connected pipes into a dispenser, thedispenser dividing the PC or PET containing the flame retardant in themolten state extruded out of the first extruder into two flows, namely,a first molten PC or PET containing the flame retardant and a secondmolten PC or PET containing the flame retardant; extruding on a secondextruder the particles of the blends of PP and/or PE and PC and/or PETto make them molten, the blends of PP and/or PE and PC and/or PET in themolten state flowing out of the second extruder and then throughsubsequent connected pipes into the dispenser, the blends of PP and/orPE and PC and/or PET in the molten state flowing into between the firstmolten PC or PET containing the flame retardant and the second molten PCor PET containing the flame retardant in the dispenser; the first moltenPC or PET containing flame retardant, the blends of PP and/or PE and PCand/or PET in the molten state and the second molten PC or PETcontaining flame retardant being superimposed together and then flowingout of the dispenser, flowing through a die head into a cooling formingroller to be cooled and formed as a sheet/film.
 2. The method of claim1, wherein the film upper layer and the film lower layer of theinsulation film are made of similar or same material.
 3. The method ofclaim 1, wherein the flame retardant in the film upper layer and thefilm lower layer of the insulation film comprises a phosphor-containingflame retardant or a silicon-containing flame retardant or abromine-containing flame retardant or a chlorine-containing flameretardant.
 4. The method of claim 3, wherein the PC or PET in the filmupper layer and the film lower layer of the insulation film accounts for75%-99.7% of a mass of the film upper layer or film lower layer, and theflame retardant accounts for 0.3-25 of the mass of the film upper layeror the film lower layer.
 5. The method of claim 4, wherein the PP and/orPE in the film intermediate layer accounts for 5%-95% of a mass of thefilm intermediate layer, the PC in the film intermediate layer accountsfor 4.5%-94.7% of a mass of the film intermediate layer and additives inthe film intermediate layer accounts for 0.3%-20% of a mass of the filmintermediate layer.
 6. The method of claim 1, wherein the thickness ofthe film intermediate layer of the insulation film is 5%-50% of thethickness of the insulation film, and the thickness of the film upperlayer and the film lower layer is 50%-95% of a total thickness of theinsulation film.
 7. The method of claim 1, wherein the total thicknessof the insulation film is in a range of 0.05 mm-3.0 mm.
 8. A method ofproducing an insulation film, wherein said insulation film comprises: afilm upper layer and a film lower layer, wherein the film upper layer ismade of PC or PET material and the film lower layer is made of PC or PETmaterial, and the PC or PET material contains a flame retardant to meetflame retardance thereof; a film intermediate layer located between thefilm upper layer and the film lower layer, wherein the film intermediatelayer is made of blends of PP and/or PE and PC; and wherein an uppersurface of the film intermediate layer is bound together with a lowersurface of the film upper layer, and a lower surface of the filmintermediate layer is bound together with an upper surface of the filmlower layer, the method comprising: on a first extruder, extruding PC orPET particles containing the flame retardant to melt them to form afirst molten PC or PET containing the flame retardant, the first moltenPC or PET containing the flame retardant flowing out of the firstextruder and then through subsequent connected pipes into a dispenser;extruding on a third extruder PC or PET particles containing the flameretardant to make them molten to form a second molten PC or PETcontaining the flame retardant, the second molten PC or PET containingthe flame retardant being extruded out of the third extruder and thenflowing through subsequent connected pipes into the dispenser; extrudingon a second extruder the particles of the blends of PP and/or PE and PCand/or PET to make them molten, the blends of PP and/or PE and PC and/orPET in the molten state flowing out of the second extruder and thenthrough subsequent connected pipes into the dispenser, the blends of PPand/or PE and PC and/or PET in the molten state flowing into between thefirst molten PC or PET containing the flame retardant and the secondmolten PC or PET containing the flame retardant in the dispenser; thefirst molten PC or PET containing flame retardant, the blends of PPand/or PE and PC and/or PET in the molten state and the second molten PCor PET containing flame retardant being superimposed together and thenflowing out of the dispenser, flowing through a die head into a coolingforming roller to be cooled and formed as a sheet/film.
 9. The method ofclaim 8, wherein the film upper layer and the film lower layer of theinsulation film are made of similar or same material.
 10. The method ofclaim 8, wherein the flame retardant in the film upper layer and thefilm lower layer of the insulation film comprises a phosphor-containingflame retardant or a silicon-containing flame retardant or abromine-containing flame retardant or a chlorine-containing flameretardant.
 11. The method of claim 10, wherein the PC or PET in the filmupper layer and the film lower layer of the insulation film accounts for75%-99.7% of a mass of the film upper layer or film lower layer, and theflame retardant accounts for 0.3-25 of the mass of the film upper layeror the film lower layer.
 12. The method of claim 11, wherein the PPand/or PE in the film intermediate layer accounts for 5%-95% of a massof the film intermediate layer, the PC in the film intermediate layeraccounts for 4.5%-94.7% of a mass of the film intermediate layer andadditives in the film intermediate layer accounts for 0.3%-20% of a massof the film intermediate layer.
 13. The method of claim 8, wherein thethickness of the film intermediate layer of the insulation film is5%-50% of the thickness of the insulation film, and the thickness of thefilm upper layer and the film lower layer is 50%-95% of a totalthickness of the insulation film.
 14. The method of claim 8, wherein thetotal thickness of the insulation film is in a range of 0.05 mm-3.0 mm.15. A method of producing an insulation film, wherein said insulationfilm comprises: a film upper layer and a film lower layer, wherein thefilm upper layer is made of PC or PET material and the film lower layeris made of PC or PET material, and the PC or PET material contains aflame retardant to meet flame retardance thereof; a film intermediatelayer located between the film upper layer and the film lower layer,wherein the film intermediate layer is made of blends of PP and/or PEand PC; and wherein an upper surface of the film intermediate layer isbound together with a lower surface of the film upper layer, and a lowersurface of the film intermediate layer is bound together with an uppersurface of the film lower layer, the method comprising: providing a filmupper layer and a film lower layer, wherein both of the film upper layerand film lower layer are made of a PC or PET material and the PC or PETmaterial contains a flame retardant to meet the flame retardancethereof; providing an intermediate layer located between the film upperlayer and the film lower layer, the film intermediate layer is made ofthe blends of PP and/or PE and PC and/or PET; applying a glue to a lowersurface of the film upper layer and/or an upper surface of the filmintermediate layer, and applying a glue on an upper surface of the filmlower layer and/or a lower surface of the film intermediate layer;delivering the film upper layer, film intermediate layer and film lowerlayer through pressing rollers to be pressed and formed as a sheet/film.16. The method of claim 15, wherein the film upper layer and the filmlower layer of the insulation film are made of similar or same material.17. The method of claim 15, wherein the flame retardant in the filmupper layer and the film lower layer of the insulation film comprises aphosphor-containing flame retardant or a silicon-containing flameretardant or a bromine-containing flame retardant or achlorine-containing flame retardant.
 18. The method of claim 17, whereinthe PC or PET in the film upper layer and the film lower layer of theinsulation film accounts for 75%-99.7% of a mass of the film upper layeror film lower layer, and the flame retardant accounts for 0.3-25 of themass of the film upper layer or the film lower layer.
 19. The method ofclaim 18, wherein the PP and/or PE in the film intermediate layeraccounts for 5%-95% of a mass of the film intermediate layer, the PC inthe film intermediate layer accounts for 4.5%-94.7% of a mass of thefilm intermediate layer and additives in the film intermediate layeraccounts for 0.3%-20% of a mass of the film intermediate layer.
 20. Themethod of claim 15, wherein the thickness of the film intermediate layerof the insulation film is 5%-50% of the thickness of the insulationfilm, and the thickness of the film upper layer and the film lower layeris 50%-95% of a total thickness of the insulation film.